1. Field of the Invention
The present invention relates to a solvent delivery device for liquid chromatography and, more particularly, to such a device which delivers solvent to a liquid chromatography column using a plunger pump.
2. Description of the Prior Art
Although conventional plunger pumps for solvent delivery devices for use in liquid chromatography are available in various kinds, that is, reciprocating single plunger pump, double plunger pump and triple plunger pump, compressibility of solvent at higher pressure has required to compensate for the change in flow rate due to solvent compression, irrespective of the kind of plunger pump used. Specifically, a compensating rate at a certain pressure corresponding to the compressibility of a solvent used is determined first, then the compensating rate is changed in proportion to the pressure so that liquid compressibility may be a linear function of pressure. In this method, the plunger speed at a certain flow rate can be given by EQU Ve'=Ve+KPVe
where Ve' is a plunger speed at a certain pressure P; Ve is a plunger speed at P=O; K is a compensating coefficient for a specific solvent. In the above formula, KPVe is a compensating plunger speed corresponding to the compensating flow rate at a certain pressure P.
Such a flow rate compensation has required that the compensating quantity be manually adjusted whenever another solvent having a different compressibility is used.
Also, in the prior art method, the velocity at which the plunger is moved for delivery is uniformly speeded up in accordance with the increase of the pressure in the plunger pump. However, such speedup of the velocity is sometimes insufficient, while the quantity of solvent compressed in the pump chamber is also increased with the increase of the pressure. Therefor, the prior art method causes to take much time for compression of solvent, delays the operation of the outlet check valve of the pump and then increases the pulsation of the solvent delivered.